50 



orbital crests, but ends vaguely in the rugae that lie between them and the 

 lateral epibranchial tooth, is deeper graven, so that the gastric region is very 

 clearly delimited from the epibranchial regions throughout. 



The epibranchial regions are quite distinctly areolated — {a) by an obliquely 

 transverse furrow near the middle ; and (b) by a sinuous groove which skirts 

 the cervical groove. 



The whole frontal region is granulous or rugose ; the epigastric crests are 

 more rugose ; nearly the anterior iialf of the gastric region is transversely 

 rugose ; all the anterior half of the lateral epibranchial regions is obliquely 

 rugose ; and the postero-lateral borders and their vicinity are abundantly 

 crossed by rugte. 



The edge of the front is more sinuous, its lateral free angles are also more 

 pronounced. 



The antero -lateral borders of the carapace are decidedly shorter than the 

 postero-lateral. 



The merus of the external maxillipeds is broader than long. 



The chelipeds are more crisply rugose, and the fingers are stouter and 

 heavier. 



The 7th abdominal segment of the male is slightly longer than broad, and 

 very blunt. 



In the largest specimen (a male) the carapace is li''« inch long. li'V inch 

 broad, and VVths inch deep. 



on 1 rj i)f\ 



. Sing Karah, Sumatra. Prof. Max Weber. 3 (J , 1 $ . 



This species also does not belong to the fauna of British India ; but as forms 

 which might be regarded as varieties of it occur in Burma, I include a diagnosis 

 of it here. 



26. PoTAMON (Potamon) pruinosum, Alcock. (Fig. 8.) 



This species resembles Potamon larnaudii more especially in the following 

 particulars : — The cervical groove is deep and distinct where it defines the 

 posterior part of the gastric region ; beyond this point it broadens out and 

 becomes shallow ; and beyond the expansion it becomes indistinct (but even 

 more indistinct than in larnaudii), and is lost in the rugosities of the antero- 

 lateral part of the epibranchial regions without cutting the post- orbital crests. 

 The eiDibranchial i^egions are, anteriorly, not well demarcated from the gastric 

 region, nor are they distinctly areolated. The antero-lateral borders of the 

 carapace (measured from tlie tip of the lateral-epibranchial tooth) are barely 

 as long as the postero-lateral. 



On the other hand, it resembles Potamon brevimarginatum in the following 



